Interpretive Summary: Cryptosporidium, an enteric protozoan parasite that infects a wide range of vertebrate hosts worldwide, is one of the most common causes of diarrhea in humans and livestock. Of the four species of Cryptosporidium routinely found in cattle only some subtypes of the species C. parvum are human pathogens. Within C. parvum numerous subtypes, based on sequences of the GP60 gene, have been identified. Therefore, it is crucial to know which ones are actually present in C.parvum -positive fecal samples from animals to determine their public health implications. In this study, C. parvum from 73 dairy calves less than two months old from Buenos Aires province (Argentina) were molecularly characterized using sequence analysis of the GP60 gene. Seventy five sequences were obtained, and seven different subtypes were identified. Three of the subtypes found in this study (IIaA16G1R1, IIaA18G1R1, and IIaA19G1R1) were previously identified in humans. A significant association was found between subtypes and geographic location, with some subtypes predominating in some locations but absent in others. There was no relation between subtypes and presence of diarrhea in the calves. These findings indicate that feces from calves containing the three zoonotic subtypes could play an important role in the transmission of cryptosporidiosis to humans in contact with these animals and their surroundings, or from contamination of surface water used for drinking, or from contamination of fresh produce where cattle feces are used for fertilizer. This information will be useful to other scientists, veterinarians and regulatory agencies.

Technical Abstract:
Cryptosporidium parvum from 73 dairy calves less than two months old from Buenos Aires province (Argentina) were molecularly characterized using sequence analysis of the GP60 gene. Seventy five sequences were obtained, and seven different subtypes were identified, all belonging to the IIa subtype family. The most common subtypes were IIaA20G1R1 (27/75), IIaA22G1R1 (16/75), and IIaA18G1R1 (13/75). Subtypes IIaA21G1R1, IIaA23G1R1, IIaA16G1R1 and IIaA19G1R1 were found sporadically. Two samples contained mixed infections with IIaA21G1R1 and IIaA22G1R1. A significant association was found between subtypes and geographic location, whereas there was no relation between subtypes and presence of diarrhea. Three of the subtypes found in this study (IIaA16G1R1, IIaA18G1R1, and IIaA19G1R1) were previously identified in humans. These findings suggest that cattle could play an important role in the transmission of cryptosporidiosis to humans in Buenos Aires province.